Apparatus for casting metal strips



Feb. 6, 1951 J. B. BRENNAN APPARATUS FOR CASTING METAL STRIPS Filed May26, 1947 ATTORNEYS fabrication to article form, such as a press orbrake.

4 Patented Feb. 6, 1,1951

UNlTED' s'r rss msasrus i -oi: cssrmo snirsnsm Joseph 1:. a iii-mum.Ohio Application May as, 1947, No. 150,441

is cum. zz-iss) This invention relates to apparatus for casting fapparatus also is adapted to practice the method metal in' strip form,especially to casting long,

thin strips of alloy metal particularly suited for a bearing, in

whereas the properties of the bearings are ordi-- narily improved ifmore lead is present. Now

only thick sections or billets of alloy metal can be cast, and theyrequire a great deal of subsequent reduction or rolling which causesundesirable lead segregation. This is also true of other alloy stripwherein different melting point metals are incorporated in the same meltfor casting. alloys ultimately to be processed to strip form.

The general object of this invention is to avoid and overcome theforegoing and other disadvantages of present apparatus for producingalloy strip and to provide novel alloy strip forming apparatuscharacterized by its rapid freezing of molten metal in strip form.

Another object of the invention is to reduce the segregation of thelower melting point metal inthe production of thin alloy metal strip.

Another object of the invention is to eliminate transfer of molten metalfrom a container therefor to a mold and to provide a metal mixingcontainer also adapted to form part of a die.

A further object of the invention is to cast a metal alloy in strip formand tosolidify such alloy rapidly when the liquid alloy is cast ormolded to the desired shape.

Another object of the invention is to provide a practical, positive,uncomplicated die for easting alloy metal in strip form withoutobJection-' able segregation of the components thereof.

Another object of the invention is to provide an apparatus for forming athin metal strip consisting of two layers of different metals.

Other objects of the invention are to provide difierent width coiledmetal strips for use in defining a die cavity, to provide a die forcasting measured quantities of metal therein, and to provide means formaintaining a pressure on the metal as it is cast.

The foregoing and other objects and advantages of the invention will bemade apparent as the specification proceeds.

Attention is directed to the accompanying drawing, wherein:

Fig. 1 is a vertical section through apparatus embodying the principlesof the invention, which of the invention; and

Fig. 2 is a bottom plan on line 2-2 of Fig. 1. Referring more in detailto the drawing, a suitable container I0, usually metal, is shown asbeing mounted on a base I I and provided for use 'in preparing liquidmetal alloys to be processed in accordance with the principles of myinvention. The container III has heating means ordinarily associatedwith it, in this instance, a helically positioned conduit I2 is formedin its base and connects to a suitable supply of heating fluid. In allevents, the container l0 has an annular chamber l3 and is adapted toreceive material therein and to heatsuch material to render or retain itfluid.

As a salient feature of my invention, Iam able to use the container'lllas one half of a forming die and avoid transfer of molten metal from thecontainer to a separate die or mold for solidification. Avoiding suchmetal transfer obviously avoids the metal flow and delay, withconsequent metal segregation, as occurs with prior casting procedure. Toachieve this. result, I provide a novel mold or die section generallyindicated at I which includes a die holder I5 that has an annular flangei6 extending therefrom designed so as to engage snugly with the chamberl3 of the container It to deflne therewith a die cavity. The die holder,II is positioned by conventional means (not shown) for movement to andfrom engagement with the container I'll. In order to form a long thinmetal strip in the die, a helical cavity I1 is provided therein.- Thiscavity i1 is formed by means of tightly coiling together'a relativelywide metal strip. l8 and a relatively narow metal strip is with theupper (as shown) edges of the strips being aligned. The strips l8 and I9are tightly wound on an arbor 2" in the position shown in Fig. 1, beingretained in such shape by a band placed therearound or by in- 'sertioninto the die holderl5. The strips l8 and I! may be secured in the dieholder in any desired manner even to being retained therein by magneticmeans, or by mechanical means, or combinations thereof. In all events,the coiled strips l8 and I9 tightly fill the die holder bethat it isexactly sufficient to flll the cavity I1.

Thus, when the last metal, such as lead, is mixed with the metal in thechamber I: to produce a homogeneous alloy, the die holder is is rapidlybrought down into engagement with the container I. and all of the metalin the chamber I3 is forced into the helical cavity l1. As soon as thedie holder II is seated in the chamber It, the heating medium flowingthrough the conduit i2 is shut oil, if it has not previously been shutoff, and cooling fluid is sprayed on the associated die holder andcontainer by nozzles 2| which are connected to a conventional supply ofa cooling medium. The foregoing procedure effects a rapid chillingaction on the material in the mold cavity, which action maybeaccelerated, if desired by flowing a coolant through the conduit II, orby forming cooling fins on the die holder and container, or by use ofother cooling means. Hence segregation of the low melting metal of thealloy is avoided since the molten metal in the chamber I3 is stirredcontinuously until the die holder I5 is engaged therewith. Conventionalvents (not shown) are formed for the mold cavity and they may comprisetiny grooves (not shown) in the narrow band I8 extending transverselythereof. The vent grooves in the band is should connect to other vents23 which may be formed in the die holder l5 for leading any entrappedgases to the atmosphere. solidified alloy in the cavity I1 is ejected byknock out pins 22 slidably carried by the die holder for unitary action.Such pins 22 may eject the solidified metal and the strips l8 and I9 asa unit to be separated thereafter in any desired manner, or the pins 22may pass through holes in the narrow strip I9 andeject only thesolidified helical cell. In the latter case, it would be preferable tohave the strips II and I9 integrally connected and suitably secured inthe die holder. Usually the strips l8 and I! are not integrally bondedor fixed in position.

The helical cavity I! may be. for example, 2

inches deep, 1; inch wide (radially) and 500 or more feet in length whenthe die holder is about 36 inches in diameter. Practice of the inventionhas produced copper-lead alloys with uniform lead distribution, when upto 20% lead has been present, with no lead particle larger than .010".

The helical alloy strip produced can be finished in any desired manner,such as by cleaning, mechanically rolling, heat treating, etc., althoughit may be used in some instances without any further shaping or formingthereof.

Adhesion between the cast material and the strips l8 and I9 is avoidedby coating them with a suitable lubricant, such as lampblack, powderedmica, graphite, or plumbago prior to each casting cycle. The extremecasting speedreduces the erosion of the apparatus to a minimum.

Pressurized strip casting can be achieved by my invention, if desired,so as to produce a line grain structure and increased tensile strength.For example, the cast metal can be subjected to any desired pressure asit is being cast if the material to be fabricated into bearings.

The container 10 can be made of any material adapted to stand the hightemperatures to which the apparatus is subjected. A material known asInconel or Inconelex, which is a high chromium nickel ferrous alloy, hasbeen used to form the wide strip IS with excellent results. For bearingalloys, the strips, it and is can be made of ordinary cold rolled stripsteel while any metal material of higher melting point than the castmaterial can be used, as a general rule. The narrow strips is can bemade from heat resistant non-metallic material, such as asbestos, orfiberglass, or combinations thereof. The strips i8 and I! can be of thesame thickness if desired, or of any desired thickness relation.

It is desirable. of course, to maintain an accurately controlledtemperature, usually only a few degrees above the melting point of thematerial, on the metal in the chamber to facilitate the rapidsolidification thereof. Usually the metal in the chamber is agitated inany conventional manner to becertain that the mixture isuniform incomposition and temperature until is of minimum length as the metal isdisplaced from a normal level position in the chamber to a helicalposition in the die holder. This substantially equal casting flowresults in an extremely uniform grain in the cast metal which has goodcharacteristics and is free from segregation of non-alloyingconstituents.

In some instances, vacuum or suction creating means may be associatedwith the apparatus embodying the invention to facilitate and assist inthe casting action and to aid in-filling the cavity. Such vacuum on thecasting cavity may be established by connection of a vacuum generator tothe vents 23 formed in the die holder i5.

In some instances, it may be desirable to use a briquet of carbon orother heat resisting material in place of the arbor 20 as a core for thehelical strips [8 and is. As the coiled strips' l8 and I9 will springout to the largest diameter possible and thus leave the center of thecoiled strips void of. material, the core for the strips i8 and i9 couldbe positioned in the container Such a iii to extend up into the chamberi3. core for the strips I8 and l9.could even originally be formed on orintegral withthe container Hi to position the molten metal in thechamber iii in annular form prior to engagement of the die holder andthe container.

The principles of the invention can be used to coat a metal strip on oneside with a different metal. This action may be achieved by substitutingtwo superimposed metal strips for the wider strip i8. Thu one surface ofeach strip would be exposed to the molten metal entering the die cavity.The surfaces of -the double thickness metal strip it, which are to bondto the cast metal, should be precleaned- A molten salt bath, for examplepotassium cyanate, is suitable for this cleaning action. Otherpreparatory steps, such as pretinning, or electroplating with copper orelectroflashing with nickel facilitates bonding copper or silver bearingmetals to steel strips in accordance with the invention.

The invention can be used in casting various metallic strips includingalloys .of aluminum, tin, copper, or lead. However, any metal orthermoplastic material can be processed in accordance with the inventionwhen one desires to produce a helical article.

The drawing shows electro-conductive coils l0 and 3| associated with theouter surfaces of the that an improved metal strip can be providedby theinvention.

One complete embodiment of the invention has i been illustrated anddescribed in detail herein. but it will be understood that the inventionis not limited to the specific example set forth since modification maybe resorted to within the scope of the appended claims.

I claim:

1. A casting mold, or die comprising two interwound helices ofheat-resisting strip material of diiferent widths, having one edge ofeach strip in the same plane, the other edge of one strip protrudingappreciably from the corresponding edge of the second strip to define ahelical mold cavity therebetween, said strips being separable tofacilitate removal of a casting therefrom.

2. In a casting mold or die, a cavity forming device consisting of twointerwound'helices of thin wide strips of heat resisting material withone edge of each of the helices being exposed to a die chamber, one ofsaid strips of material being wider than the other, said exposed edgesbeing spaced axially of the mold from each other to expose a portion ofone helix and define a helical cavity between adjacent surfaces thereoffor forming a thin wide strip therein.

3. An article as in claim 2 wherein said strips are separate and saidstrip that is partially exposed is thinner than the other strip whichdetermines the thickness of the die cavity.

4. In a matrix for forming thin-strip metal in long lengths, thecombination of a matrixbody different widths in edge alignment woundinto a spiral, one edge only of each tape comprising said spiral beingin the same plane, opposite edges of each tape being in substantiallydifferent planes, both faces of the narrower tape being in facialcontact with only a portion of the faces of the wider tape, theremaining portions of the faces of the wider tape defining a hollowhelical groove in conjunction with the unaligned. edge of the narin thesame plane as the other edge of the wider tape.

6. In a matrix for forming thin strip metal, a pair of thin flexibleheat resistant tapes one of which is about several inches wider than theother, said narrower tape being approximately in. thick and with saidwider tape being thinner than the other said tape, said tapes beinghelicomprising two thin metal tapes of substantially cally positioned ina unit in abutting face to face relationship to each other, said tapesbeing positioned with'one lateral section and edge of said wider tapeprotruding from said unit and defining a narrow relatively deep moldcavity therebetween,said strips being separable after a molding actiontofacilitate removal of a cast strip therefrom.

7. In a matrix for forming thin strip metal, a pair'of thin flexibleheat resistant tapes one of which is appreciably wider than the other,said narrower tapebeing thicker than the other said tape, each of saidtapes being positioned in a plurality of helical convolutions with theconvolutions of each tape forming alternate laminae in a unit inabutting face to face relation to each other, said tapes beingpositioned with one lateral section and edge of said wider tapeprotruding from said unit and defining a narrow relatively deep moldcavity therebetween, said strips being separable after a moldingactionto facilitate removal of a cast strip therefrom.

8. In a matrix for forming thin strip metal, a pair of thin flexiblemetal tapes one of which is appreciably wider than the other, each ofsaid tapes being positioned in a plurality of helical convolutions withthe convolutions of each tape forming alternate laminae in a unit inabutting face to face relation to each other, said tapes beingpositioned with one lateral section and edge of said wider tapeprotruding from said unit and defining a narrow relatively deep moldcavity therebetween, said strips being separable after a molding actionto facilitate removal of a cast strip therefrom.

9. In a matrix for forming thin strip metal, a pair of thin relativelywide flexible heat resistant tapes, said tapes being of differentwidths, said tapes being superimposed and being helically positioned ina unit in abutting face to face relationship to each other, said tapesbeing positioned with one lateral section and edge of one said tapeprotruding from said unit and defining a narrow relatively deep moldcavity therebetween.

10. A matrix as in claim 7 wherein said unit is positioned with'itslongitudinal axis extending substantially vertically and with saidcavity being open from the lower surface of the matrix, and vent meansin said unit and communicating with the upper portion of said cavity.

JOSEPH B. BRENNAN.

nnrannncas CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Martin July 23, 1946

